Gender differences exist in the neuroendocrine control of GH secretion in humans and animals. The regulatory mechanisms that drive such sex differences are not known, but presumptively are estrogen dependent. We plan to study the potency & efficacy of somatostatin's inhibition of GH release in postmenopusal women on and off estrogen. Novel insights into the specific neuroendocrine mechanisms of estrogen action will help explicate the physiological coupling between sex-steriods and the GH axis in health and disease.